1. Field of the Invention
This invention relates to a radiation image read-out method and apparatus, wherein stimulating rays are irradiated to a stimulable phosphor sheet, on which a radiation image has been stored, and light, which is emitted by the stimulable phosphor sheet when the stimulable phosphor sheet is exposed to the stimulating rays, is photoelectrically detected, an image signal representing the radiation image being thereby obtained. This invention particularly relates to a radiation image read-out method and apparatus, wherein the stimulating rays are linearly irradiated to the stimulable phosphor sheet, and the light emitted by the stimulable phosphor sheet is detected with a line sensor.
2. Description of the Related Art
Radiation image recording and reproducing systems, wherein a stimulable phosphor sheet, which comprises a substrate and a layer of a stimulable phosphor overlaid on the substrate, have heretofore been widely used in practice.
With the radiation image recording and reproducing systems, a stimulable phosphor sheet is exposed to radiation carrying image information of an object, such as a human body, and a radiation image of the object is thereby recorded on the stimulable phosphor sheet. Thereafter, stimulating rays, such as a laser beam, are caused to scan the stimulable phosphor sheet in two-dimensional directions. The stimulating rays cause an exposed area of the stimulable phosphor sheet to emit light in proportion to the amount of energy stored thereon during its exposure to the radiation. The light emitted from the exposed area of the stimulable phosphor sheet, upon stimulation thereof, is photoelectrically detected and converted into an electric image signal by photoelectric read-out means.
The image signal, which has been obtained from the radiation image recording and reproducing systems described above, is then subjected to image processing, such as gradation processing and processing in the frequency domain, such that a visible radiation image, which has good image quality and can serve as an effective tool in, particularly, the efficient and accurate diagnosis of an illness, can be obtained. The image signal having been obtained from the image processing is utilized for reproducing a visible image for diagnosis, or the like, on film or displaying a visible image for diagnosis, or the like, on a cathode ray tube (CRT) display device. In cases where the stimulable phosphor sheet, from which the image signal has been detected, is then exposed to erasing light, and energy remaining on the stimulable phosphor sheet is thereby released, the erased stimulable phosphor sheet is capable of being used again for the recording of a radiation image.
Also, a novel radiation image recording and reproducing system aiming at enhancement of a detection quantum efficiency in the formation of the radiation image, i.e., a radiation absorptivity, a light emission efficiency, an emitted light pickup efficiency, and the like, wherein a novel type of stimulable phosphor sheet is utilized, has been proposed in, for example, Japanese Patent Application No. 11(1999)-372978. With the novel type of the stimulable phosphor sheet utilized in the proposed radiation image recording and reproducing system, the radiation absorbing functions and the energy storing functions of the conventional stimulable phosphor sheet are separated from each other.
The novel type of the stimulable phosphor sheet utilized in the proposed radiation image recording and reproducing system contains a layer of a stimulable phosphor for energy storage, which is capable of absorbing light having wavelengths falling within an ultraviolet to visible region and thereby storing energy of the light having wavelengths falling within the ultraviolet to visible region, and which is capable of being stimulated by light having wavelengths falling within a visible to infrared region and thereby radiating out the stored energy as emitted light.
The novel type of the stimulable phosphor sheet should preferably take on the form combined with a layer of a phosphor for radiation absorption, which is capable of absorbing radiation and being caused to emit light having wavelengths falling within an ultraviolet to visible region. In such cases, energy from the light having wave lengths falling within the ultraviolet to visible region, which light is emitted from the layer of the phosphor for radiation absorption when the layer of the phosphor for radiation absorption is exposed to the radiation carrying image information of an object, (the amount of the energy corresponding to the radiation image information) is stored on the layer of the stimulable phosphor for energy storage. When the stimulable phosphor sheet, on which the radiation image has thus been stored, is scanned with the stimulating rays, the light carrying the radiation image information is emitted from the layer of the stimulable phosphor for energy storage.
The novel type of the stimulable phosphor sheet need not necessarily be provided with the layer of the phosphor for radiation absorption. In such cases, the novel type of the stimulable phosphor sheet is utilized in combination with a fluorescent screen, which is provided with the layer of the phosphor for radiation absorption capable of absorbing radiation and being caused to emit the light having wavelengths falling within the ultraviolet to visible region.
Specifically, in such cases, the fluorescent screen is kept in close contact with the novel type of the stimulable phosphor sheet, and the radiation carrying the image information of the object is irradiated to the fluorescent screen. As a result, the light having wavelengths falling within the ultraviolet to visible region is emitted from the layer of the phosphor for radiation absorption of the fluorescent screen. Also, energy from the light emitted from the phosphor for radiation absorption (the amount of the energy corresponding to the radiation image information) is stored on the layer of the stimulable phosphor for energy storage of the stimulable phosphor sheet. When the stimulable phosphor sheet, on which the radiation image has thus been stored, is scanned with the stimulating rays, the light carrying the radiation image information is emitted from the layer of the stimulable phosphor for energy storage.
Novel radiation image read-out apparatuses for use in the radiation image recording and reproducing systems described above have been proposed in, for example, Japanese Unexamined Patent Publication Nos. 60(1985)-111568, 60(1985)-236354, and 1(1989)-101540. In the proposed radiation image read-out apparatuses, from the point of view of keeping the emitted light detection time short, reducing the size of the apparatus, and keeping the cost low, a line sensor comprising a charge coupled device (CCD) image sensor, or the like, is utilized as the photoelectric read-out means.
Basically, the radiation image read-out apparatuses of such types comprise:
i) stimulating ray irradiating means for linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a line sensor, which comprises a plurality of photoelectric conversion devices arrayed along the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and
iii) sub-scanning means for moving the stimulable phosphor sheet with respect to the stimulating ray irradiating means and the line sensor and in a direction (a sub-scanning direction), which is approximately normal to a length direction of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays (a main scanning direction).
The stimulating ray irradiating means for linearly irradiating the stimulating rays onto the stimulable phosphor sheet in the manner described above may be constituted so as to produce fan beam-like stimulating rays. Alternatively, the stimulating ray irradiating means may be constituted so as to deflect a thin beam and to cause the deflected thin beam to linearly scan the stimulable phosphor sheet.
However, with the conventional radiation image read-out apparatuses, wherein the stimulating ray irradiating means, which linearly irradiates the stimulating rays to the stimulable phosphor sheet, and the line sensor are utilized, the problems have heretofore been encountered in that an efficiency, with which the light emitted by the stimulable phosphor sheet is collected, cannot be kept high.
The primary object of the present invention is to provide a radiation image read-out method, in which stimulating ray irradiating means and a line sensor are utilized, wherein an efficiency, with which light emitted by a stimulable phosphor sheet is collected, is capable of being kept high.
Another object of the present invention is to provide an apparatus for carrying out the radiation image read-out method.
A first radiation image read-out method in accordance with the present invention is characterized by guiding light, which has been emitted by a stimulable phosphor sheet, with a light guide device, which receives the emitted light with one surface and guides the emitted light toward end faces, and receiving the guided light with a line sensor, an efficiency with which the emitted light is collected being thereby enhanced. Specifically, the present invention provides a first radiation image read-out method, comprising the steps of:
i) linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, with stimulating ray irradiating means, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) receiving the light, which has been emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, with one surface of a light guide device, which is located such that the one surface stands facing the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, the emitted light, which has thus been received, being guided through the light guide device toward end faces of the light guide device,
iii) detecting the emitted light, which has been radiated out from at least one end face of the light guide device, with a line sensor, which comprises a plurality of photoelectric conversion devices arrayed along the at least one end face of the light guide device, and
iv) moving the stimulable phosphor sheet with respect to the stimulating ray irradiating means, the light guide device, and the line sensor and in a direction, which is approximately normal to a length direction of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays.
A second radiation image read-out method in accordance with the present invention is characterized by guiding light, which has been emitted by a stimulable phosphor sheet, with a light guide device (i.e., a fluorescent light guide device), which receives the emitted light with one surface, converts the emitted light into fluorescence, and guides the fluorescence toward end faces, and receiving the guided fluorescence with a line sensor, an efficiency with which the emitted light is collected being thereby enhanced. Specifically, the present invention also provides a second radiation image read-out method, comprising the steps of:
i) linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, with stimulating ray irradiating means, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) receiving the light, which has been emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, with one surface of a light guide device, which is located such that the one surface stands facing the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, the emitted light, which has thus been received, being converted by the light guide device into fluorescence, the fluorescence being guided through the light guide device toward end faces of the light guide device,
iii) detecting the fluorescence, which has been radiated out from at least one end face of the light guide device, with a line sensor, which comprises a plurality of photoelectric conversion devices arrayed along the at least one end face of the light guide device, the emitted light being thereby detected indirectly, and
iv) moving the stimulable phosphor sheet with respect to the stimulating ray irradiating means, the light guide device, and the line sensor and in a direction, which is approximately normal to a length direction of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays.
In the second radiation image read-out method in accordance with the present invention, the intensity of the fluorescence is in proportion to the intensity of the light emitted by the stimulable phosphor sheet. Therefore, in cases where the intensity of the fluorescence is detected with the line sensor, the intensity of the light emitted by the stimulable phosphor sheet, i.e. the radiation image having been stored on the stimulable phosphor sheet, is capable of being detected.
Each of the first and second radiation image read-out methods in accordance with the present invention should preferably be modified such that each of two line sensors is located at one of two end faces of the light guide device, which end faces stand facing each other, such that each of the two line sensors is capable of detecting the light, which is emitted from an approximately overall length of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and
outputs of photoelectric conversion devices of the two line sensors, which photoelectric conversion devices correspond to an identical site on the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, are added to each other. (As for the second radiation image read-out method in accordance with the present invention, the term xe2x80x9cdetecting emitted lightxe2x80x9d as used herein means that the emitted light is detected indirectly through the detection of the fluorescence.)
Alternatively, each of the first and second radiation image read-out methods in accordance with the present invention may be modified such that the line sensor is located at one end face of the light guide device, such that the line sensor is capable of detecting the light, which is emitted from an approximately overall length of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and
an end face of the light guide device, the end face being located on a side opposite to the one end face at which the line sensor is located, is formed as a light reflecting surface.
As another alternative, each of the first and second radiation image read-out methods in accordance with the present invention may be modified such that at least one line sensor is located at a region of one end face of the light guide device, such that the at least one line sensor is capable of detecting the light, which is emitted from a subarea of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays,
a region of the one end face of the light guide device, at which region no line sensor is located, is formed as a light reflecting surface,
at least one line sensor is located at a region of a different end face of the light guide device, which different end face stands facing the one end face of the light guide device, such that the at least one line sensor stands facing the region of the one end face of the light guide device, which region is formed as the light reflecting surface, and
a region of the different end face of the light guide device, at which region no line sensor is located, is formed as a light reflecting surface.
Also, each of the first and second radiation image read-out methods in accordance with the present invention should preferably be modified such that the light guide device is divided into pixels, which are arrayed along an array direction of the photoelectric conversion devices of the line sensor and at a pitch identical with an array pitch of the photoelectric conversion devices.
Further, each of the first and second radiation image read-out methods in accordance with the present invention should preferably be modified such that the light, which has been emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, is collected with a light collecting optical system, and the emitted light, which has thus been collected, is guided by the light collecting optical system toward the light guide device.
In such cases, each of the first and second radiation image read-out methods in accordance with the present invention should more preferably be modified such that the light, which has been emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, is collected with a plurality of light collecting optical systems, and the emitted light, which has thus been collected, is guided by each of the light collecting optical systems toward the light guide device.
Furthermore, in each of the first and second radiation image read-out methods in accordance with the present invention, the stimulable phosphor sheet may be a stimulable phosphor sheet having both the functions for radiation absorption and the functions for energy storage. Alternatively, the stimulable phosphor sheet may be a stimulable phosphor sheet provided with a layer of a stimulable phosphor for energy storage.
In cases where the stimulable phosphor sheet is a stimulable phosphor sheet provided with the layer of the stimulable phosphor for energy storage, the stimulable phosphor sheet may also be provided with a layer of a phosphor for radiation absorption. Alternatively, in such cases, the stimulable phosphor sheet may not be provided with the layer of the phosphor for radiation absorption and may be utilized in combination with a fluorescent screen having the layer of the phosphor for radiation absorption.
As will be understood from the specification, it should be noted that the term xe2x80x9cmoving a stimulable phosphor sheet with respect to stimulating ray irradiating means, a light guide device, and a line sensorxe2x80x9d as used herein means movement of the stimulable phosphor sheet relative to the stimulating ray irradiating means, the light guide device, and the line sensor, and embraces the cases wherein the stimulable phosphor sheet is moved while the stimulating ray irradiating means, the light guide device, and the line sensor are kept stationary, the cases wherein the stimulating ray irradiating means, the light guide device, and the line sensor are moved while the stimulable phosphor sheet is kept stationary, and the cases wherein both the stimulable phosphor sheet and the stimulating ray irradiating means, the light guide device, and the line sensor are moved. In cases where the stimulating ray irradiating means, the light guide device, and the line sensor are moved, they should be moved together with one another.
The present invention further provides an apparatus for carrying out the first radiation image read-out method in accordance with the present invention. Specifically, the present invention further provides a first radiation image read-out apparatus, comprising:
i) stimulating ray irradiating means for linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a light guide device, which is located such that one surface stands facing the linear area of the stimulable phosphor sheet exposed to the linear stimulating grays, the light guide device receiving the light, which has been emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, with the one surface of the light guide device and guiding the emitted light, which has thus been received, toward end faces of the light guide device,
iii) a line sensor, which comprises a plurality of photoelectric conversion devices arrayed along at least one end face of the light guide device, the line sensor detecting the emitted light, which has been radiated out from the at least one end face of the light guide device, and
iv) sub-scanning means for moving the stimulable phosphor sheet with respect to the stimulating ray irradiating means, the light guide device, and the line sensor and in a direction, which is approximately normal to a length direction of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays.
The present invention still further provides an apparatus for carrying out the second radiation image read-out method in accordance with the present invention. Specifically, the present invention still further provides a second radiation image read-out apparatus, comprising:
i) stimulating ray irradiating means for linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a light guide device, which is located such that one surface stands facing the linear area of the stimulable phosphor sheet exposed to the linear stimulating grays, the light guide device receiving the light, which has been emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, with the one surface of the light guide device, converting the emitted light, which has thus been received, into fluorescence, and guiding the fluorescence toward end faces of the light guide device,
iii) a line sensor, which comprises a plurality of photoelectric conversion devices arrayed along at least one end face of the light guide device, the line sensor detecting the fluorescence, which has been radiated out from the at least one end face of the light guide device, and thereby indirectly detecting the emitted light, and
iv) sub-scanning means for moving the stimulable phosphor sheet with respect to the stimulating ray irradiating means, the light guide device, and the line sensor and in a direction, which is approximately normal to a length direction of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays.
Each of the first and second radiation image read-out apparatuses in accordance with the present invention should preferably be modified such that each of two line sensors is located at one of two end faces of the light guide device, which end faces stand facing each other, such that each of the two line sensors is capable of detecting the light, which is emitted from an approximately overall length of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and
the apparatus further comprises addition processing means for performing addition processing on outputs of photoelectric conversion devices of the two line sensors, which photoelectric conversion devices correspond to an identical site on the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays. (As for the second radiation image read-out apparatus in accordance with the present invention, the term xe2x80x9cdetecting emitted lightxe2x80x9d as used here in means that the emitted light is detected indirectly through the detection of the fluorescence.)
Alternatively, each of the first and second radiation image read-out apparatuses in accordance with the present invention may be modified such that the line sensor is located at one end face of the light guide device, such that the line sensor is capable of detecting the light, which is emitted from an approximately overall length of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and
an end face of the light guide device, the end face being located on a side opposite to the one end face at which the line sensor is located, is formed as a light reflecting surface.
As another alternative, each of the first and second radiation image read-out apparatuses in accordance with the present invention may be modified such that at least one line sensor is located at a region of one end face of the light guide device, such that the at least one line sensor is capable of detecting the light, which is emitted from a subarea of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays,
a region of the one end face of the light guide device, at which region no line sensor is located, is formed as a light reflecting surface,
at least one line sensor is located at a region of a different end face of the light guide device, which different end face stands facing the one end face of the light guide device, such that the at least one line sensor stands facing the region of the one end face of the light guide device, which region is formed as the light reflecting surface, and
a region of the different end face of the light guide device, at which region no line sensor is located, is formed as a light reflecting surface.
Also, each of the first and second radiation image read-out apparatuses in accordance with the present invention should preferably be modified such that the light guide device is divided into pixels, which are arrayed along an array direction of the photoelectric conversion devices of the line sensor and at a pitch identical with an array pitch of the photoelectric conversion devices.
Further, each of the first and second radiation image read-out apparatuses in accordance with the present invention should preferably be modified such that the apparatus further comprises a light collecting optical system, which is located between the stimulable phosphor sheet and the light guide device, the light collecting optical system collecting the light, which has been emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and guiding the emitted light, which has thus been collected, toward the light guide device.
In such cases, each of the first and second radiation image read-out apparatuses in accordance with the present invention should more preferably be modified such that the light, which has been emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, is collected with a plurality of light collecting optical systems, and the emitted light, which has thus been collected, is guided by each of the light collecting optical systems toward the light guide device.
Furthermore, in each of the first and second radiation image read-out apparatuses in accordance with the present invention, the stimulable phosphor sheet may be a stimulable phosphor sheet having both the functions for radiation absorption and the functions for energy storage. Alternatively, the stimulable phosphor sheet may be a stimulable phosphor sheet provided with a layer of a stimulable phosphor for energy storage.
In cases where the stimulable phosphor sheet is a stimulable phosphor sheet provided with the layer of the stimulable phosphor for energy storage, the stimulable phosphor sheet may also be provided with a layer of a phosphor for radiation absorption. Alternatively, in such cases, the stimulable phosphor sheet may not be provided with the layer of the phosphor for radiation absorption and may be utilized in combination with a fluorescent screen having the layer of the phosphor for radiation absorption.
The inventors conducted extensive research and found that the problems with regard to a low efficiency, with which the light emitted by the stimulable phosphor sheet is collected, occur due to the problems in that a light receiving width of a CCD line sensor, or the like, which light receiving width is taken in the direction approximately normal to the array direction of the photoelectric conversion devices constituting the CCD line sensor, or the like is smaller than a light emission width on the stimulable phosphor sheet, which light emission width is taken in the sub-scanning direction.
Specifically, ordinarily, the light receiving width of the CCD line sensor, or the like, which light receiving width is taken in the sub-scanning direction, is at most approximately 25 xcexcm. Also, ordinarily, the light emission width on the stimulable phosphor sheet, which light emission width is taken in the sub-scanning direction, falls within the range of approximately 100 xcexcm to approximately 500 xcexcm. In the conventional radiation image read-out apparatuses, wherein an erect equi-magnification optical system is employed as the optical system for collecting the light emitted by the stimulable phosphor sheet, the width of the emitted light, which impinges upon the light receiving surface of the line sensor, falls within the range of approximately 100 xcexcm to approximately 500 xcexcm. Therefore, a large portion of the emitted light impinges upon positions outward from the light receiving surface of the line sensor.
However, with the first radiation image read-out method and apparatus in accordance with the present invention, the light having been emitted by the stimulable phosphor sheet is caused to enter from the surface of the light guide device into the light guide device and is guided through the light guide device toward the end faces of the light guide device. Therefore, in cases where the width of the surface of the light guide device is set to be comparatively large, the light, which has been emitted with the large light emission width from the stimulable phosphor sheet, is capable of efficiently impinging upon the surface of the light guide device. Also, the emitted light, which has been radiated out from the at least one end face of the light guide device, is received by the line sensor. Therefore, in cases where the thickness of the end face of the light guide device is set to be approximately identical with the light receiving width of the line sensor or slightly smaller than the light receiving width of the line sensor, a large portion of the emitted light, which has been radiated out from the end face of the light guide device, or approximately all of the emitted light is capable of being received by the line sensor.
With the second radiation image read-out method and apparatus in accordance with the present invention, the light having been emitted by the stimulable phosphor sheet is caused to enter from the surface of the light guide device into the light guide device. Therefore, in cases where the width of the surface of the light guide device is set to be comparatively large, the light, which has been emitted with the large light emission width from the stimulable phosphor sheet, is capable of efficiently impinging upon the surface of the light guide device.
Also, with the second radiation image read-out method and apparatus in accordance with the present invention, the emitted light, which has entered into the light guide device, is converted by the light guide device into the fluorescence. The fluorescence is guided through the light guide device toward the end faces of the light guide device, and the fluorescence, which has been radiated out from the at least one end face of the light guide device, is received by the line sensor. Therefore, in cases where the thickness of the end face of the light guide device is set to be approximately identical with the light receiving width of the line sensor or slightly smaller than the light receiving width of the line sensor, a large portion of the fluorescence, which has been radiated out from the end face of the light guide device, or approximately all of the fluorescence is capable of being received by the line sensor.
As described above, with the first radiation image read-out method and apparatus in accordance with the present invention and the second radiation image read-out method and apparatus in accordance with the present invention, the efficiency, with which the light emitted by the stimulable phosphor sheet is collected, is capable of being kept markedly higher than with the conventional radiation image read-out apparatuses. Therefore, a read-out image signal having a high signal-to-noise ratio is capable of being obtained, and a radiation image having good image quality is capable of being reproduced.
The first radiation image read-out method and apparatus in accordance with the present invention and the second radiation image read-out method and apparatus in accordance with the present invention may be modified such that each of two line sensors is located at one of two end faces of the light guide device, which end faces stand facing each other, such that each of the two line sensors is capable of detecting the light, which is emitted from an approximately over all length of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays. Also, in such cases, the outputs of the photoelectric conversion devices of the two line sensors, which photoelectric conversion devices correspond to an identical site on the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, are added to each other. With the modifications described above, the emitted light, which has entered into the light guide device and has traveled toward one of the two end faces of the light guide device, or the fluorescence, which has been produced from excitation with the emitted light within the light guide device and has traveled toward one of the two end faces of the light guide device, is detected by the line sensor, which is located at the one end face of the light guide device. Also, the emitted light, which has entered into the light guide device and has traveled toward the other end face of the light guide device, or the fluorescence, which has been produced from the excitation with the emitted light within the light guide device and has traveled toward the other end face of the light guide device, is detected by the line sensor, which is located at the other end face of the light guide device.
Therefore, in cases where the outputs of the photoelectric conversion devices of the two line sensors, which photoelectric conversion devices correspond to an identical site on the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, are added to each other, the total sum of the intensity of the emitted light, which has traveled toward the one end face of the light guide device, and the intensity of the emitted light, which has traveled toward the other end face of the light guide device, or the total sum of the intensity of the fluorescence, which has traveled toward the one end face of the light guide device, and the intensity of the fluorescence, which has traveled toward the other end face of the light guide device, is capable of being obtained. Accordingly, the efficiency, with which the light emitted by the stimulable phosphor sheet or the fluorescence is detected, is capable of being enhanced. In the second radiation image read-out method and apparatus in accordance with the present invention, the fluorescence is detected, and the emitted light is thus detected indirectly. Therefore, in the cases of the second radiation image read-out method and apparatus in accordance with the present invention, the enhancement of the efficiency, with which the fluorescence is detected, leads to the enhancement of the efficiency, with which the light emitted by the stimulable phosphor sheet is detected.
Also, the first radiation image read-out method and apparatus in accordance with the present invention and the second radiation image read-out method and apparatus in accordance with the present invention may be modified such that the line sensor is located at one end face of the light guide device, such that the line sensor is capable of detecting the light, which is emitted from an approximately overall length of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays. Further, in such cases, an end face of the light guide device, the end face being located on a side opposite to the one end face at which the line sensor is located, is formed as the light reflecting surface. With the modifications described above, the emitted light, which has entered into the light guide device and has traveled toward the side opposite to line sensor, or the fluorescence, which has been produced from excitation with the emitted light within the light guide device and has traveled toward the side opposite to the line sensor, is reflected from the light reflecting surface toward the line sensor. Therefore, the emitted light or the fluorescence is capable of being efficiently detected by the line sensor.
Further, the first radiation image read-out method and apparatus in accordance with the present invention and the second radiation image read-out method and apparatus in accordance with the present invention may be modified such that at least one line sensor is located at a region of one end face of the light guide device, such that the at least one line sensor is capable of detecting the light, which is emitted from a subarea of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and a region of the one end face of the light guide device, at which region no line sensor is located, is formed as the light reflecting surface. Also, in such cases, at least one line sensor is located at a region of a different end face of the light guide device, which different end face stands facing the one end face of the light guide device, such that the at least one line sensor stands facing the region of the one end face of the light guide device, which region is formed as the light reflecting surface, and a region of the different end face of the light guide device, at which region no line sensor is located, is formed as the light reflecting surface. With the modifications described above, the light reflecting surface is formed at the region of the end face of the light guide device, which region stands facing the line sensor located at the region of the opposite end face of the light guide device. Therefore, the emitted light, which has entered into the light guide device and has traveled toward the side opposite to line sensor, or the fluorescence, which has been produced from excitation with the emitted light within the light guide device and has traveled toward the side opposite to the line sensor, is reflected from the light reflecting surface toward the line sensor. Accordingly, the emitted light or the fluorescence is capable of being efficiently detected by the line sensor.
Furthermore, the first radiation image read-out method and apparatus in accordance with the present invention and the second radiation image read-out method and apparatus in accordance with the present invention may be modified such that the light, which has been emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, is collected with the light collecting optical system, and the emitted light, which has thus been collected, is guided by the light collecting optical system toward the light guide device. With the modifications described above, the light emitted by the stimulable phosphor sheet is capable of being collected and detected more efficiently. In particular, such effects are capable of being obtained markedly in cases where a plurality of light collecting optical systems are utilized.